1. Field of the Invention
The present invention relates to refrigerant handling systems and, in particular, to the user interface for such systems. The invention relates specifically to user interfaces which include a display screen and selective input keys.
2. Description of the Prior Art
Many types of user interfaces for automatically operating devices are well known in the art, including interfaces which incorporate a display screen and user-operable input keys. Some systems have display screens which display only status of the system, while others are interactive in that they prompt and respond to user actions, including actuation of the selective input keys. Interactive display screens typically include a plurality of dots or pixels which are independently controllable for displaying a wide variety of alphanumerical or graphical images. Such display screens are typically CRT displays, although other types of displays, such as LCD displays are commonly used. In some of these interactive display screens, certain ones of the selective input keys are software definable keys or "soft keys". Such keys are typically disposed respectively immediately adjacent to different regions of the display screen, and the function of the key varies with the message displayed in the associated screen region.
Non-interactive display screens can be of simplified construction, since they are commonly used to display only a few characters or lines of text. For these applications, text-based display screens have been used, since they are of very simple and economical construction. Interactive display screens, on the other hand, are typically of much more expensive and complicated CRT or LCD type, which offer much greater flexibility in the types of messages or graphical material which can be displayed. Text-based display screens have not been used in interactive applications because of their limited capabilities and because they are typically provided on a dedicated circuit board which has a wide margin around the display screen and, therefore, prevents the positioning of keys, such as soft keys, closely adjacent to the display screen.